#!/usr/bin/env python3.3

#
#  Filename: e15.py
#  Author  : lukas singer
#
#  Comment : Created by createSolution.sh
#            Lattice paths

#import euler
#from euler import *

grid=20
l={(0,0):1}
def pe15():
  for i in range(grid+1):
    for j in range(grid+1):
      if i==0 or j==0:
        l[(i,j)]=1
      else:
        l[(i,j)]=l[(i-1,j)]+l[(i,j-1)]
  print(l[grid,grid])

if __name__=="__main__":
  pe15()

